Even ray tracing does not capture all physics of electromagnetism and only works at the level of geometrical optics: any effect, like diffraction or iridescence

Even ray tracing does not capture all physics of electromagnetism and only works at the level of geometrical optics: any effect, like diffraction or iridescence, that arises due to the wave-like nature of light still need to be implemented in ad-hoc way in a ray tracing algorithm. But fully simulating Maxwell's equations (or QFT) to keep track of those minor effects would be insanely expansive.